1. Field of the Invention
The present invention relates to a method for determining the presence of a residue within a fingerprint using mass spectrometric techniques.
2. Background Information
Latent fingerprints contain numerous compounds, such as naturally occurring compounds from the body, e.g., cholesterol, squalene and fatty acids, or compounds which may be left on the latent fingerprint from a contact, e.g., cocaine or other drugs of abuse, as discussed in, for example: R. S. Ramotowski, in: H. C. Lee and R. E. Gaensslen (Eds.) Advances in Fingerprint Technology (2nd Ed.), CRC Press, Boca Raton, Fla., 2001, page 63 (hereinafter, the “Ramotowski reference”); K. G. Asano, C. K. Bayne, K. M. Horsman and M. V. Buchanan, J. Forensic Sci., 47, (2002), pages 1-3 (hereinafter, the “Asano reference”); and N. E. Archer, Y. Charles, J. A. Elliott. and S. Jickells, “Changes in the lipid concentration of latent fingerprint residue with time after deposition on a surface.” Forensic Sci. Int. (Article in Press) (hereinafter, the “Archer reference”). Of the studies to date with this objective, use has been made of Raman spectroscopy, as discussed in, for example: J. S. Day, H. G. M. Edwards, S. A. Dobrowski and A. M. Voice, “The detection of Drugs of Abuse in Fingerprints using Raman Spectroscopy I: Latent Fingerprints,” Spectrochimica Acta A, 60 (2004), page 563 (hereinafter, the “first Day reference”); and J. S. Day, H. G. M. Edwards, S. A. Dobrowski and A. M. Voice, “The detection of Drugs of Abuse in Fingerprints using Raman Spectroscopy I: Cyanoacrylate-Fumed Fingerprints,” Spectrochimica Acta A, 60 (2004), page 1725 (hereinafter, the “second Day reference”).
In these studies, difficulty was observed in visually locating the drugs of abuse in order to perform the analysis and the method was also relatively insensitive and relatively non-specific. The most common method for the interrogation of latent fingerprints is Gas Chromatography-Mass Spectrometry (GC-MS). It has previously been shown that residues from latent fingerprints can be extracted into a solvent and analyzed by GC-MS, as discussed in, for example, the Asano and Archer references. Such compounds include squalene and cholesterol, however, levels of these on latent fingerprints vary, not only between individuals, but between times for the same individual, as discussed in, for example, the Archer reference. GC-MS has also been used to detect contact residues, such as cocaine from spiked fingerprints, with a limit of detection of approx 300 μg (as described in, for example, J. P. Nielson and A. I. Katz, “A Processing Protocol for Drug Residue and Latent Print Evidence,” J. Forensic Sci., 33 (1998), pages 1463-1472 (hereinafter, the “Nielson reference”)) and for the detection of drugs of abuse and metabolites from commercial sweat patches down to ng per patch levels (as described in, for example, M. A. Heustis, J. M. Oyler, E. J. Cone, A. T. Wstadik, D. Schoendorfer and R. E. Joseph, “Sweat Testing for Cocaine, Codeine and Metabolites by Gas Chromatoraphy-Mass Spectrometry,” J. Chromatogr. B. 733 (1999), page 247 (hereinafter, the “Heustis reference”)) and from saliva (as described in, for example, D. A. Kidwell, J. C. Holland and S. Athanaselis, “Testing for Drugs of Abuse in Saliva and Sweat,” J. Chromatogr. B. 713 (1998), page 111 (hereinafter, the “Kidwell reference”)). However, all of the above-mentioned methods require complicated extraction procedures to be undertaken prior to analysis.
Matrix-Assisted Laser Desorption/Ionization Mass Spectrometry Time-Of-Flight Mass Spectrometry (MALDI-TOF-MS) was developed in late 1980s by Karas and Hillenkamp, and has become established as a technique for the analysis and accurate molecular weight determination of large macromolecules such as proteins, polysaccharides, nucleic acids and synthetic polymers with high mass accuracy and extreme sensitivity. MALDI is a “soft” ionization process that produces minimum fragmentation, and in which the energy from the laser is spent in volatilizing the matrix rather than in degrading the macromolecule. MALDI-TOF-MS has not been considered in the field of identifying residues present on latent fingerprints. MALDI-TOF-MS is termed Surface Assisted Laser Desorption/Ionization (SALDI) when graphite, titanium dioxide or silica are used as suspension matrices for MALDI, as described in, for example: J. Sunner, E. Dratz and Y. C. Chen, “Graphite Surface-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry of Peptides and Proteins from Liquid Solutions,” Anal. Chem. 67 (1995), page 4335 (hereinafter, the “Sunner reference”); and A. Crecelius, M. R. Clench, D. S. Richards and V. Parr, “Thin-Layer Chromatography-Matrix-Assisted Laser Desorption Ionisation-Time-of-Flight Mass Spectrometry Using Particle Suspension Matrices,” J. Chromatogr. A. 958 (2002), page 249 (hereinafter, the “Crecelius reference”).